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authorFlorian Weimer <fweimer@redhat.com>2015-10-02 11:34:13 +0200
committerFlorian Weimer <fweimer@redhat.com>2015-10-02 11:34:13 +0200
commit676599b36a92f3c201c5682ee7a5caddd9f370a4 (patch)
tree6860752c26ccab76ee9db5e60ff465d1edf25feb /gshadow
parentb0f81637d5bda47be93bac34b68f429a12979321 (diff)
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Harden putpwent, putgrent, putspent, putspent against injection [BZ #18724]
This prevents injection of ':' and '\n' into output functions which use the NSS files database syntax. Critical fields (user/group names and file system paths) are checked strictly. For backwards compatibility, the GECOS field is rewritten instead. The getent program is adjusted to use the put*ent functions in libc, instead of local copies. This changes the behavior of getent if user names start with '-' or '+'.
Diffstat (limited to 'gshadow')
-rw-r--r--gshadow/Makefile2
-rw-r--r--gshadow/putsgent.c11
-rw-r--r--gshadow/tst-putsgent.c168
3 files changed, 180 insertions, 1 deletions
diff --git a/gshadow/Makefile b/gshadow/Makefile
index 883e1c8..c811041 100644
--- a/gshadow/Makefile
+++ b/gshadow/Makefile
@@ -26,7 +26,7 @@ headers = gshadow.h
routines = getsgent getsgnam sgetsgent fgetsgent putsgent \
getsgent_r getsgnam_r sgetsgent_r fgetsgent_r
-tests = tst-gshadow
+tests = tst-gshadow tst-putsgent
CFLAGS-getsgent_r.c = -fexceptions
CFLAGS-getsgent.c = -fexceptions
diff --git a/gshadow/putsgent.c b/gshadow/putsgent.c
index 0b2cad6..c1cb921 100644
--- a/gshadow/putsgent.c
+++ b/gshadow/putsgent.c
@@ -15,9 +15,11 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <gshadow.h>
+#include <nss.h>
#define _S(x) x ? x : ""
@@ -29,6 +31,15 @@ putsgent (const struct sgrp *g, FILE *stream)
{
int errors = 0;
+ if (g->sg_namp == NULL || !__nss_valid_field (g->sg_namp)
+ || !__nss_valid_field (g->sg_passwd)
+ || !__nss_valid_list_field (g->sg_adm)
+ || !__nss_valid_list_field (g->sg_mem))
+ {
+ __set_errno (EINVAL);
+ return -1;
+ }
+
_IO_flockfile (stream);
if (fprintf (stream, "%s:%s:", g->sg_namp, _S (g->sg_passwd)) < 0)
diff --git a/gshadow/tst-putsgent.c b/gshadow/tst-putsgent.c
new file mode 100644
index 0000000..5b0f381
--- /dev/null
+++ b/gshadow/tst-putsgent.c
@@ -0,0 +1,168 @@
+/* Test for processing of invalid gshadow entries. [BZ #18724]
+ Copyright (C) 2015 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <gshadow.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static bool errors;
+
+static void
+check (struct sgrp e, const char *expected)
+{
+ char *buf;
+ size_t buf_size;
+ FILE *f = open_memstream (&buf, &buf_size);
+
+ if (f == NULL)
+ {
+ printf ("open_memstream: %m\n");
+ errors = true;
+ return;
+ }
+
+ int ret = putsgent (&e, f);
+
+ if (expected == NULL)
+ {
+ if (ret == -1)
+ {
+ if (errno != EINVAL)
+ {
+ printf ("putsgent: unexpected error code: %m\n");
+ errors = true;
+ }
+ }
+ else
+ {
+ printf ("putsgent: unexpected success (\"%s\")\n", e.sg_namp);
+ errors = true;
+ }
+ }
+ else
+ {
+ /* Expect success. */
+ size_t expected_length = strlen (expected);
+ if (ret == 0)
+ {
+ long written = ftell (f);
+
+ if (written <= 0 || fflush (f) < 0)
+ {
+ printf ("stream error: %m\n");
+ errors = true;
+ }
+ else if (buf[written - 1] != '\n')
+ {
+ printf ("FAILED: \"%s\" without newline\n", expected);
+ errors = true;
+ }
+ else if (strncmp (buf, expected, written - 1) != 0
+ || written - 1 != expected_length)
+ {
+ printf ("FAILED: \"%s\" (%ld), expected \"%s\" (%zu)\n",
+ buf, written - 1, expected, expected_length);
+ errors = true;
+ }
+ }
+ else
+ {
+ printf ("FAILED: putsgent (expected \"%s\"): %m\n", expected);
+ errors = true;
+ }
+ }
+
+ fclose (f);
+ free (buf);
+}
+
+static int
+do_test (void)
+{
+ check ((struct sgrp) {
+ .sg_namp = (char *) "root",
+ },
+ "root:::");
+ check ((struct sgrp) {
+ .sg_namp = (char *) "root",
+ .sg_passwd = (char *) "password",
+ },
+ "root:password::");
+ check ((struct sgrp) {
+ .sg_namp = (char *) "root",
+ .sg_passwd = (char *) "password",
+ .sg_adm = (char *[]) {(char *) "adm1", (char *) "adm2", NULL},
+ .sg_mem = (char *[]) {(char *) "mem1", (char *) "mem2", NULL},
+ },
+ "root:password:adm1,adm2:mem1,mem2");
+
+ /* Bad values. */
+ {
+ static const char *const bad_strings[] = {
+ ":",
+ "\n",
+ ":bad",
+ "\nbad",
+ "b:ad",
+ "b\nad",
+ "bad:",
+ "bad\n",
+ "b:a\nd",
+ ",",
+ "\n,",
+ ":,",
+ ",bad",
+ "b,ad",
+ "bad,",
+ NULL
+ };
+ for (const char *const *bad = bad_strings; *bad != NULL; ++bad)
+ {
+ char *members[]
+ = {(char *) "first", (char *) *bad, (char *) "last", NULL};
+ if (strpbrk (*bad, ":\n") != NULL)
+ {
+ check ((struct sgrp) {
+ .sg_namp = (char *) *bad,
+ }, NULL);
+ check ((struct sgrp) {
+ .sg_namp = (char *) "root",
+ .sg_passwd = (char *) *bad,
+ }, NULL);
+ }
+ check ((struct sgrp) {
+ .sg_namp = (char *) "root",
+ .sg_passwd = (char *) "password",
+ .sg_adm = members
+ }, NULL);
+ check ((struct sgrp) {
+ .sg_namp = (char *) "root",
+ .sg_passwd = (char *) "password",
+ .sg_mem = members
+ }, NULL);
+ }
+ }
+
+ return errors;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"